Intravesical therapy is said to be therapeutic when it is used to kill visible tumor cells. Some patients are unable to have their entire tumor(s) removed with TURBT because of the location or extent of the tumor. Intravesical therapy in these patients is designed to kill the remaining tumor and is thus called therapeutic. Intravesical therapy is also considered therapeutic when used to treat carcinoma in situ.
Many patients receiving intravesical therapy have already had their entire tumor removed by TURBT. The goal of this type of treatment is prophylactic (i.e., trying to prevent the growth of new tumors). Most experts believe that this type of treatment actually works not by protecting you from the development of new tumors, but by eradicating microscopic tumors that would eventually have grown into larger tumors.